Although it is important to discuss any exposure that you are worried about with your primary care physician
, I don't think you could have contracted HIV from this type of exposure. The little splotches of red on your French fries are more likely to be dried Ketchup than blood. The second reason why this is unlikely is that HIV cannot survive in dried blood for any reasonable amount of time. Most likely all the viruses, if they were there, would be dead. The third reason is the fact that exposure to the virus through the mouth is not a usual way through which HIV is transmitted. The virus needs access to your blood stream which it would not have in your mouth. By the time it reached the stomach it would be dead.
Again, I suggest that you discuss any exposure that you are worried about with your primary care physician. He or she can determine whether any exposure to blood or other bodily fluids in the future increases your risk of developing a blood borne infection. Finally, you should probably be tested for the HIV virus at least once in your life regardless of any of your exposures. This is a universal recommendation from the Centers for Disease Control (CDC).