Congratulations on completing your surgeries. Tell your doctor everything. I'm not sure if it is, just a guess, having no experience in this surgery, but may be a black and blue from surgery, injury from such moving the tongue, securing it during surgery, anetsesia material, even chlohexidine rinse, if taking that, can cause the the tongue to turn color black, teeth also. Best bet is to call your surgeons office, visit.
Good luck.
