I am about to (slowly) start lamotrigine. but i noticed a small no-itchy rash. do i need to wait until the rash clears up first?

Since lamotrigine can cause a life threatening rash, it is started slowly with low dose titration over time. A preceding rash would not necessarily preclude usage, but have this evaluated by your doctor just to be on the safe side, first. It is not feasible to accurately predict how a potential skin co-morbidity might interact with a new drug.