I agree with Tmac and Arutha. They’ve pointed out the most common problems. A dirty or sticky hairspring and magnetism probably being the most common reasons that I can think of. There are other reasons a watch can run fast such as more than one coil sitting between regulator pins, regulator pin adjustment etc. but would first check the things they’ve suggested. If that all looks good then please let us know a bit more about how fast it’s running as this can help us figure out what may be going on.