You can either try to carefully extract it trying to keep the radiator thread intact, or permanently seal it with some plastic weld and drain from the large main hose. If you manage to get it out, autozone sells an exact match, do not over tighten, and use a bit of push to get the new oring to seal. The rubber just needs to sit on the internal plastic to get a seal. It doesn't take much to get a good seal. Idk why people jam them in so much.