What is this?!

I have a 7 week old son who is usually pretty content however today he has been unusually fussy but I put it down to wind as he does occasionally struggle. I laid him in his cot for maybe 2 minutes(?) whilst I went to tend to his sister, but he was never alone he was left with his dad! Dad and I did a swap of as big sister wanted daddy snuggles before bed. I picked up my little boy and I noticed blood in the corner of his mouth so I pulled out my torch on my phone and seen this in the very back of his mouth ... (this was once the bleeding had stopped)

There’s nothing he could have caught his mouth on and we never put our fingers in his mouth! Bleeding has now stopped, he’s settled and still able to latch and feed from the breast. Should I try get in touch with a doctor or see how he goes tonight?

Thanks.