Help! I found a ball python in the wild

[WingedWolfPsion]

They aren't fond of being stroked--unlike mammals or birds, they never express physical affection. They're solitary animals in the wild. Once he is settled with proper heat, leave him alone entirely for a week, then offer him a live rodent--a rat is usually best. It should be as big around as the widest part of the snake. Observe carefully so that the rat doesn't harm the snake and don't leave them unattended (rats can injure or kill snakes that aren't interested in eating), and remove it in 1/2 hour if it's not eaten. If the rat is rejected, try a mouse.

A couple of days after he eats, you may handle him. Pick him up and hold him until he relaxes and begins to explore. He will probably just try to slither away, which is normal. If you handle him for 1/2 hour sessions each day, except when he is due to eat, has just eaten, or is getting ready to shed, he will come out of his shell and calm down. A tame ball pythons is comfortable around people, but does not seek out attention--they don't enjoy handling, but they do get very used to it. This makes things less stressful for them when they must be handled to check for health issues, for cage cleanings, etc. They are extremely shy animals.
I expect the click was just him forcing air out of his lungs quickly as he tensed up, but keep an ear out for audible breathing, any sign of bubbles or mucous around his mouth or nose, rasping, or resting with the head elevated--these things are signs of a respiratory infection, which would require prompt veterinary attention. In general, snakes shouldn't make sounds.