Hi welcome to health care magic........
It would have been good if you have mentioned your age.
Anyhow a lump in a male breast , one sided is a matter of concern if you are aged adult. It may be a normal varient if you are an adolescent .
I would suggest u go to a surgeon get it examined-
1) Get a FNAC of the lump i.e the pathologist puts a needle into the lump and tales a small piece of it and examines it in the microscope that can tell us what the lump is all about.
If its a normal breast tissue u can undergo plastic surgery
and get the lump removed.