I was going to mention ingrown toenail too. I injured my toe at Karate a few years ago (did a very bad kick...ouch!) Didn't think too much of it at the time but ended up getting the pain you describe - like a sharp sting when you put pressure on it. Discovered I had an ingrown toenail. The side of my toenail had curled right under and it has been the very devil to try and straighten out. What I do is keep my toenails really short and gently ease the curled bit out (it does hurt), then trim it off. I've been doing this for a few months now and my toenail is gradually straightening out again. I don't get the pain anymore. Sometimes it was so bad it kept me awake at night.

Definitely see a chiropodist (podiatrist) as they will know what to do.