im sorry. I know it sux... I am in somewhat of a similar situation. I was using a glycolic wash and was in the Bahamas 3 months ago. Guess it caused sensitivity.I had sun block on but I thnk I sweat it off and now have my cheek somewhat darker than the rest of my face.. Been ove 3 months actually. Derm said its sun damage and it goes away but takes a long time...I am assuming yours will also go but take a long time...
I once had a burn from something and it took over a year to completely go...Right now I am using something called Jason Ester C skin ton balancer. I just started it last week so dont know how it works. I am also using 15% glycolix paRAB (I am assuming you dont want glycolic acid.)
You should see your derm. May prescribe a llightener or something...Good luck !