Yes — wax that fully blocks the ear canal is a well-recognised, fully reversible cause of tinnitus. The mechanism is straightforward: the blockage acts like an earplug, reducing the input reaching the cochlea, and the brain responds by turning up its internal gain in the same way it does after permanent hearing loss. Remove the wax and, for many people, the tinnitus that came with it goes away within hours to a few days.
A few important caveats. Do not use cotton buds — they push wax deeper and can perforate the eardrum. Do not use ear candles; they do not work and cause burns. Olive oil drops for a week, followed by professional irrigation or micro-suction if needed, is the right pathway. If tinnitus persists after wax removal, that is a sign there is something else going on, and you should book a hearing test.
And if your tinnitus came on without any sense of fullness or muffled hearing, wax is unlikely to be the cause; do not delay a real workup by chasing it.