Hard to say really. A random bump could be any number of things. I suggest the next time this appears, you go immediately to have it swabbed by PCR at an urgent care or a doctor. Don’t wait to be seen.
Since blood came out of it, it doesn’t sound like hsv. Hsv blisters/lesions are surface sores with a clear or yellowish fluid.
Still, since it has returned a few times, that’s enough reason for me to advise you getting checked.
If the appearance of this sore coincides with recent sexual activity, you could also do a blood test if it has been at least 12 weeks. You would want an IgG test.