arduino uno error

i accidently uploaded the sketch on arduino as isp while the board selected was arduino mega 2560, and now the ide is giving the error avrdude stk500_getsync(): not in sync resp=0x30 and sometimes it says the signature of the microcontroller is incorrect so i connected another m328 preloaded with arduino ide but the same error persists. also somebody tell me how to overcome he problem of wrong signature on other microcontrollers cause i read that it is very common to happen with the microcontrollers but the avrdude keeps on rejecting them giving the "yikes" or the "signature" message even if we know that the mc we are using is pefectly fine! also i have connected all the wires correctly and checked them well power was correct in short everything else was fine!!!!!

kindly give the solution quickly since the date of my project submission approaches thanks in advance!!!!

What do the RX and TX lights do when you try to upload a sketch?