Do i have to replace it or buy a new uno or what.
As Gerben has said, that "golden thing" is a resettable fuse (AKA polyfuse).
It's there to protect the USB port of your computer against excess current draw from a faulty board (which seems to be happening, by the way).
If nothing else is connected to the Arduino and the polyfuse keeps tripping, then the fault root cause is probably a short-circuit in the board. From here there are 2 possible scenarios:
Least likely: an external agent (metallic flakes, dirt, or something like that) might be causing the short-circuit. Inspect the board, clean it and electrically isolate it when plugging it again (avoid the solder joints getting in contact with a conductive surface, use a case or a mat).
More likely: a component has failed in short-circuit mode and is causing the excess current draw that trips the polyfuse. In that case you could try to debug the board (with at least a multimeter, and maybe other instruments) to locate the faulty component and replace it. That's not an easy task unless you precisely know what to do and where to look in the board. You might be better off buying a new board.
If you want to give the repair route a try, check this question. The schematic may be of some help to you. You might want to verify the integrity of the decoupling capacitor in first place.