You might have dropped something on your foot and a nail may be disfigured from that point on – keep clipping it and let it grow out as well as it can. Trauma can affect how it grows out.
Clip the nails straight across the top frequently (if you cannot reach them, there is a long reach tool). You can use a file to file down the sharp edges over the tops and the thickness, You might get ingrown toenails. For that, slide dental floss under the nail and add more layers of the floss to pull it up from the skin (you can look for a different type of product at the store, but floss works pretty well and is easy). Wear shoes that are loose on top (big toe box) so not to push the nail further into the skin. You might want to protect the toe while it is vulnerable. It might take a week or so for relief, but you should start to feel better. You can clip and/or file the side of the toenail that is pushing into the skin. If it is a thick toenail that you can't even see how it's digging in, you're unlikely to get floss underneath - you need to have that Ingrown side cut off. If you cannot resolve the toenail pain – you can go to a specialist and have the sides of the nail trimmed off. I had this done years ago to one nail and never have had another issue with that one. It was painful to get the numbing shot in the bottom of the foot, but the relief was worth it - though the shot these days Is more localized.
To keep fungus from growing on the toes or under the nails, I wash my feet daily, dry them and drop tea tree oil on each toenail as a preventative. If you have toenail fungus, you should Google a product that can help – but look at reviews, as many products do not work. Make sure to change your socks every day and take your shoes off to allow your feet to air out - try to keep them dry most of the time. Constant sweat and moisture are a breeding ground for fungus. If fungus Is bad, ask your doctor If more agressive treatment is needed (medication, nail removal, etc.)
I put lotion on my feet after the tea tree oil, to keep the skin from cracking. Feet dry out easily and the skin cracks. But for many, the retention of moisture by keeping shoes on all day can cause the fungus to start growing. Put your foot up to a mirror to check the bottom a couple times a year unless you have concerns - then more often. I had a dermatology check-up and they found a black spot under my foot which they felt needed a biopsy. It wasn't melanoma as I always wear socks and shoes. The biopsy determined it was a bunch of strange cells, but they wanted the entire mass taken out so It would not grow back. I was told all should be fine unless it comes back, so look under the foot every so often. The removal of the mass for biopsy was painful - so I asked someone to hold my foot still. It was painful for days. I needed to apply Vaseline daily and put a bandage over it (to protect it, to keep it clean, to keep it from rubbing on my sock or shoe, and to keep a hard scab from growing on it). If you cannot do a good job clippping the toenails, go to a podiatrist to have the staff do the clipping of toenails for you. It can help prevent ingrown toenails and other potential Issues. If you have thick toenails, you can try urea solution on It - after a shower or washing your feet, file the top layer off and then apply the urea solution. Another thing you can try is putting Vick's Vapo-Rub on the toenails daily and It may help. If you have Issues with your feet or toes that don't heal or you can't reverse, go see your doctor or a specialist. There are many more Issues I have no familiarity with, nor extreme cases. I can only offer what I have found works for me or my family.
Start doing prevention on your feet and toes early and you can prevent issues from happening that make you miserable, or unable to undo. Foot and toenail care should be part of a daily routine.