I got a rash after going in the sun

I have been taking meds approximatley 3 weeks with no problem...After sunning on beach 3 weeks laterI t appeared that I was sun burned on my arms only......As the days went on I developed a rash on both of my arms.. One arm is worse than the other.. It is a week later and rash has worsened..... The warnings on the bottle of meds said be careful of overexposure to sunlight.. The 2nd bottle did not.........What did the warning mean???

Could this be what the rash is....It is burning and itching..Have never had problems in the sun before...

Any info would be appreciated...

thank you

Paul Goldschlager