4 years post op - can feel implant towards lower part of the breast - can almost pop it in and out (sort of like air bubble)

I am 4 years post op with under the muscle implants (tear drop), I have had no issues at all however I have recently felt what feels like a lump but since realised it’s the edge of my implant on my right breast. It’s right towards the scar at the bottom and I can almost push it in and out like a small air bubble that pops back and forth. Is this normal? I haven’t lost a dramatic amount of weight and never noticed this before. No pain, redness and looks the same from the outside still.