4yrs post op breast implants, 10days ago whilst doing tricep dip exercise I felt a pop feeling on my sternum. What have I done?

I'm not sure what happened to you but I doubt there was anything done to the breast implants. Report your plastic surgeon for a physical examination However.

Most likely a muscle strain; you did not do anything to harm your implants.  Treat as any other muscle pain and if it does not resolve in a reasonable period of time, see your doctor.

Probably either a small muscle strain/tear or perhaps even a small scar band that tore. Either way, the implants themselves and the result should not be affected. With time and maybe some antiinflammatory you should be fine.

I agree that you probably did no harm to yourself, the implants, or to the eventual outcome.  Exercising after Breast Aug is generally a good thing.  You need to listen to your body to prevent overdoing itIn this case your body is telling you to take it slowGood luck

You may have a muscle strain however the history of a pop suggest the possibility of a tear in the breast implant capsule.I suggest you revisit your plastic surgeon as soon as you can make an appointment.