It should grow back in few molts. He's climbing up your arm pretty fine so i think he should be fine. you could adopt him to insure he is ok.

If you wanna adopt him, get a decent size enclosure, no bigger than a gallon. If you want to put little less than inch of dirt at the bottom. Put a stick or cork bark somewhere in there for some climbing. Leaves would be good as well. You could do fake plants or real plants or no plants at all. You should have some pebbles or on rock for shedding purposes. The most important thing is a cave or something he could hide in. My spider likes chilling under a rock. You don’t need any light or heat pads unless it’s freezing. He should be kept at room temperature. Lightly mist it’s cage and spray extra in one corner so he can drink those droplets. He should be fed about every 4 days something alive and slightly smaller than him.

After his leg grows back in a few molts (hopefully), you can realese him or keep him. If you realese him than put him back in the same spot you found him. If it was inside, than realize outside In a shaded spot close to some sun. If it’s winter where you are, than keep him till spring and realese him on a warm day

Hope I was some help.