Ouch chaos, ingrown nails are horrible at the best of times - I hope this settles down for you and doesn't get too nasty...

I would see a podiatrist ASAP - try to get a recommendation if you know anyone who's seen one - but don't even take your shoe off until you've explained about the CRPS to them! Make sure they agree to ask before they even touch your foot, and that they need to explain what they are going to do before coming anywhere near you. Take the good old CRPS fact sheet too, and ask them if they might have time to look at it before they see you again .

Take the vitamin C daily as well as a spread prevention tactic, although hopefully this can be resolved without it starting the symptoms up there too.

Reall good luck and I hope it eases soon.

Bram.