Well, I want you to think about this first. Did the other person have HIV at the time? If not, then you just got some blood in your mouth.
Now, if the person did have HIV at the time, then you may have a problem. See, the saliva in your mouth is actually capable of rendering HIV harmless. However, if you have a cut in your mouth you can contract the virus. So, if the person did have HIV at the time go get tested.