What kind of spider is it...?

i found a small spider on my ceiling about 1/4 of an inch across. it is almost all dark brown/black and it is plump and hairy. its legs are fairly thick too, as well as its mandables. and it has a red boomerang shape on its abdomen. my mom thougt its a brown recluse, i thought it was a baby tarantula. we live in southern california. if anyone can help me out here i need to find out asap. i may have been bitten by it as well. thank you.