Hmm, don't want to worry you but......
In my job, dog bites are an occupational hazard. I have tended to be lucky, in that I am very dog friendly, and most dogs, if they can smell me, realise this. There have been one or two tho who seemed friendly then bit me.
One such dog didn't like me petting it after a while and gave me a warning bite on the hand. It left marks, but didn't even break the skin.
However two days later (initial sign was itching) my hand grew to gigantic proportions (imagine a blown up rubber glove) and I had to have anti biotics and a tetanus.
Better to be safe than sorry.
BTW this dog was a run of the mill family pet from a good home, not a mangy stray.