I have a small mysterious rash on my hand in between my thumb and pointer finger on my right hand. what should i do?

Contact rash?: Seeing a dermatologist is the best way to get an answer but the commonest causes come from allergic/irritant reactions to something being held with a pincer grip, such as plucking plant leaves, especially evening primrose. Topical cortisone creams may provide quick symptom relief. If not, definitely see a physician or mid-level provider.