There is not time limitation to settle your claim. If you need additional surgery, you may not want to settle the claim now, wait until the doctor says you are stationary. However, you could settle your claim now. Depending on the settlement agreement made by you with your insurance carrier, you could settle but then you would have to be responsible for paying for your surgery bills. So if you really think you don't need any additional surgery, you could settle your claim now. If you think you really do need the additional surgery, you can wait until you are declared stationary from your doctor.
The thing is that if you keep dragging this claim out, your adjuster may decide to do surveillance on you and set an Independent Medical Examination with another doctor to have you declared stationary and then any settlement would be considerably less especially if they get you rather active on surveillance. A lot of doctors are quite happy to do surgery even though it may not really be needed.
So settling your claim is really up to you. If you feel you need the surgery, I would not settle as you will be responsible for all the bills. Another point is that settlement also depends on the statutory laws in your state. However, you have a lawyer, you are paying him/her so talk to your attorney, that is what you are paying them for. And let him know about the doctor visit.
Also, most states have some sort of statutes regarding future medical care, maintenance care and the possibility of reopening your claim in the future for more active treatment. Again, talk to your attorney.