My 12 year old recently was bitten by our cat and now has a red track running up into his forearm.  Should I be concerned about this?  If I took him to the doctors, what could they do for him?

You should seek immediate medical attention for your son.  Cat bites typically carry a higher risk of infection rate and it sounds like your son has a well-developed infection that is quickly spreading.  The physician will begin him immediately on antibiotics and be able to determine how deep the infection is and if surgery is needed to better clean the wound.