Men do not develop proper breasts. They are much smaller than women's and cannot breastfeed. At puberty boys' breasts get bigger and there can be a bump under the nipple. This is a gland which appears due to hormones and is no cause for alarm. Some boys squeeze the gland to avoid growing breasts. Squeezing will not affect breast size and the gland will disappear over time whether you squeeze or not.
Attribution: Straight Talk Foundation