Some chameleons will hold their head up high after they have
been drinking and it can be perfectly normal. It seems to help
them deal with the water. However, if they get too much water
all at once or if some of the water has gone into the
lungs it will hold its head up too.
Why do you think he may have something in his throat?
Do you have a substrate in the cage? Do you have a live plant in
the cage? Could it have ingested anything that it shouldn't have?
If you have a live or fake plant in the cage, did you wash it
well before you put it in?
Did you put a container of sand in the cage in case it is a
female?
You said that it won't even try to bite you, would it try this
when you first got it? It must open its mouth when its
drinking...you could try slipping something in
between its teeth while its mouth is open then. Be careful
though...you don't want to hurt its teeth or mouth. I have
heard of people using one of those flexible
(kitchen) spatulas....but don't use it for food after if you do!
Be careful that you don't stress it out too much. Some senegals
just can't take a lot of "attention".
Hope all turns out to be "nothing"!