It's been a while since you posted, so you've probably already gone on over to the ER. But if you're still home, and if you get to feeling dizzy, have rapid breathing, or get kinda clamy, you could go into shock, so unless the ER is close by, you'll need someone to drive you over there or call 9-1-1. When you go into shock, you faint, so not good to drive. But if you feel pretty good, and you vomit blood again, then go on over to the ER. It can indicate some rather serious stuff. If you wait until you can see your doc with an emergency squeeze-in appointment on Monday, he'll probably send you over to the ER anyway. Could be something fairly simple like erosion in the upper digestive tract, like a bleeding ulcer, or something disastrous like liver failure, and your doc would not necessarily know how to treat the more complex reasons for vomiting blood.
Yes, you should probably be checked out as soon as possible. If you have a nurse on call line available to you from your insurance company or your local hospital you could call them and provide more detail. They could help you determine if you need seen right now or if you could wait until morning and see your PCP.