i got a sunburn while on this medication

I am taking this medication for mild acne treatment. i take it twice a day as directed by my dermatologist. yesterday was memorial day and it was a cool/windy but very clear and sunny day! I completely forgot my sunscreen and i got really burned in places i NEVER burned before. My HANDS my fingers and knuckles! My knees, CHEST, NOSE, forehead and FEET ! every time i go near water my hands and feet specially hands feel so tingly and sensitive and the water feels ice cold as if its going inside my skin and burning me. will getting a sunburn as i described while on this medication harm me in any specific way? i am worried about whether it will change my DNA. i used to tan easily but being on this medication it completely screwed up my skin. also, will my skin become immune to it after taking it for 2 months? my doc. says to stay on it to make sure my acne doesn't return but i don't like being on any kinds of meds! please help!!! what am i at risk for and what will happen if i stop this medication??