You sound very anxious, and you're obviously a caring Dad who is doing a great job caring for his son.
If he is crying a lot he might be coming down with something. He could be incubating an illness, when kids start to get sick, they have a personality transplant and tend to be moody, wittery and cry a lot. (I remember feeling very angry at my eldest son when he was very small, as he was crying angrily all day, then later he had the most awful tummy bug, I really felt guilty for being mad!!)
He may have trapped his finger in something without you noticing, little ones are very inquisitive and often poke their fingers in places they shouldnt. If he sounds like he is in a lot of pain, it might be worth getting A and E to check him. Babies bones are soft and easily bruised, he might not have done anything that looked terrible at the time, but it may need a doc to take a look, just in case.
Don't feel bad, accidents happen, and we tend to blame ourlseves. My youngest sprayed weedkiller in his mouth a couple of summers ago, I felt like the worst parent in the world!!!
Get the finger looked at, and I would give him a dose of baby paracetamol, in case hes incubating a cold and has a headache!
