Near anus a small bump its like small balloon its get swallon when i run but after taking antibiotic ampilox it gets smaller its soft.wht is it.

Antibiotics: Ampiclox is a combination of Ampicillin and cloxacillin, both penicillin derivatives and of broad enough spectum of activity to be partially treating a variety of infections. You need to have this examined to be sure it is as localized as you think it is, and probably it needs to be opened and drained to effect resolution. Go see your doctor.