FWIW, I suffered with ingrown toenails on the big toe of both feet for DECADES. Literally. From my teen years until I was around 50 years old. They would get so darned sore I could hardly get my socks & shoes on and once I did they were still so painful I could hardly stand to walk. Over the years I tried everything. OTC remedies, stuffing cotton under the edge of the nail to lift it up & make it grow out OVER the skin, letting them grow long, cutting them back short, trimming them every shape & way that you can think of. Nothing really worked for any length of time. They'd get ingrown and sore again within two or three weeks.
I finally went and saw a podiatrist and he fixed the problem once and for all - in less than an hour. He numbed each toe with a shot of Novocaine, and then trimmed a little more than 1/8" off the edge of the nail that was ingrown - all the way down to the cuticle. Then he put some acid on a swab and applied it to the cuticle where he had trimmed the edge of the nail away. The acid kills the cells in the cuticle at the root of the nail-bed - the structure/cells that the nail actually grows from.
It was totally painless at the time and my toes were both sore and tender for about a week while they healed, but in the five years since I haven't had a single day of pain or problem with them. It was the BEST thing I have ever done for my feet and I'd do it again in a New York minute. I just wish I hadn't waited and suffered with them for 30-40 years before actually getting the problem fixed permanently.