There is clicking noise in the pipe after I flushed my toilet bowl. The clicking sounds like a creaking door. It is rapid at first and then it slows down to a stop. Seems to be coming from within the walls, but can't pinpoint where. This is happening even in summer. I just hope it isn't like the pipe is about to burst.

I wouldn't worry too much about a pipe bursting. It won't happen.'
The noise isn't coming from the inside of the tank is it? Is it coming from the inside of the bowl?
If you're sure it comes from the pipes in the wall then perhaps it's caused by contraction and expansion.
Knocking, popping, creaking and crackling pipes are a common complaint, especially in colder weather. I can tell you what's happening and take the mystery out of it but you're not going to like the repair. When a draw is made on a hot water line the line expands against a pipe strap next to a stud and when you drain hot water from your tub or shower it goes into a chase that is a little cooler then room temperature. The heat expands the pipe causing it to rub against the stud to which it is pipe strapped. This is the sound you hear. As it cools it contracts and the noise is heard again. To repair it you must tear open the walls and locate the pipe strap that's causing the problem and shim it tight. Most people when they learn what causes it just elect to live with it. Good luck and thank you for rating my answer. Tom