If you are experiencing this from taking test, you need to get on a SERM, ASAP, to reduce activity at the estrogen receptor. Along with this, you need to get on an AI, like adex. If you are using deca or tren, skip the SERM and go staight to the adex.
If you naturally have puffy nipples, you may have naturally occouring gyno. Lowering your body fat may help. That would be the first thing I would do. If this does not help, your only option may be to have it removed through surgery.