In all probability the yellow skin you are mentioning is the scab which has formed as the skin is healing.
Most of the sunburns are second degree burns or less and usually heal without much scarring.
In your case the best course of action is to wait for a few days and let the scab separate. You can apply an antibiotic ointment like mupirocin
cream on it. If it does not become dry by 5-6 days then you should go and consult a dermatologist