Got a hit in back of the head, but mysteriously i have a bump in the front of my head(forehead)explanations?

i was grappling brazilian ju jitzu, and someone accidentally collided his back of his head with mine, and it rocked me for a second, and then i felt a lil amnesia , but than felt fine, could it be a concussion?,, idk, my forehead now is getting super swollen almost like a hematoma, but not quite that big, so i think it might be serious, bump looks lil red.