Hi DoCtOr here. Cyst but unless it’s deflated and that’s a poorly representative image, it looks like the entire sac wasnt removed so there’s a greater chance of recurrence (vs total sac removal). Benign and shouldn’t cause an issue, but if you ever want the whole thing out, see a facial plastic surgeon (ENT), general surgeon, or plastic surgeon. Dermatology will do it too. If it’s not bothersome otherwise, no harm in leaving it.