But it bothers you enough for you to keep "fiddling" with it, doesn't it? You implant pocket is well-healed (though not completely matured and softened) at 3 1/2 months post-op. With more time, this may settle, but it will definitely NOT do so if you keep "popping it in and out." Your implant pocket may have a small "tear" or hernia in the tissue layers here, and the bump is the implant protruding through that internal area of relative weakness.
It is of absolutely no concern as this is a function of your implant being felt through this weakness or "bubble" in your capsule (much like a weak spot ballooning out in an inner tube). If you stop causing the implant to protrude partially through this area, it may well scar down and even out over time, which is what the body naturally does around a round implant. Even if it doesn't, this is not a breast mass, a tumor, or a problem.
If it bugs you enough, your surgeon can close off that weak area with sutures, but of course that takes an operation. I'd leave it alone, stop "checking it," and worry not a bit! Good luck!