two of my oscars are fighting........... they were lip locking and one of them has an injury on the lip..(quite bad) im wondering if it would heal or will it give a bad effect on the fish??????????

Its hard to tell without seeing a photo of the damage.
As a precaution, you might want to treat the tank for a good week with Melafix just in case. Make sure you remove and discontinue use of any Carbon in your filter first. (You shouldn't use carbon routinely anyway, so leave it out.) As important, you need to maintain excellent water quality for the fish to heal so double up on water changes. Instead of weekly (if you are) do them every second day or so for a while. Keeping the water excellent goes a long way towards helping an injured Oscar hear. Watch the wound closely for signs of Fungus and treat for that if it becomes evident. You can then use Pimafix in addition to the Melafix and both are "natural" remedies. Other Meds will work too...
Post a photo if you can.