How Do I Stop My Shetland Pony From Biting Me ? .?

Im 15 i Have A 8 year old shetlandd stallion hes 9hh , hess been abused i rescued him ive had Storm for a year now and he has a biting problem where he nips like when im brushing himm or just standing near byy hes not bad for it but id like to stop it.