|"Computer was working fine until i decided to clean dust out of it"|
How did you go about cleaning it? One of the worse things you can do is use a vacuum because a static charge can build up within the hose & wreak havoc with the electrical components.
"I removed cpu and damaged pins beyond repair"
Bent pins generally aren't a problem, if you're careful, they can be straigtened & the CPU reused. I'm guessing you snapped some of them off? How the heck did you manage that?
"I bought another cpu and fitted it correctly"
Did you buy the exact same CPU? If not, are you sure the replacement is compatible with your motherboard? When you reinstalled the heatsink/fan, did you thoroughly clean the bottom of the heatsink & apply a small dab of thermal compound to the top of the CPU?
"now red & green light stay on with no beep sound"
Cases have different color lights so red or green means nothing. The fact that there's no beep is not a good sign though. The problem is most likely with the CPU or the motherboard.