Hair can also be countable when you refer to the individual strands of hair. "I found a couple of gray hairs."

Thanks much to all of you. Now I can get it clearly 😊

Thank all so much 😄 I can understand now

If you use the uncountable version of hair in this context, it would mean that you have a large quantity of hair in your throat. The more likely scenario is that a person has a hair (one piece of hair) in their throat. Although I suppose either is possible.

Another possible answer to 2 is "some hairs" at the back of my throat, again emphasizing the individual strands, rather than the big mass of hair that people have on top of their heads.