it has no engine light on but engine making noise and knocking whats the issue?

The 'engine' light is related to emissions (pollution/exhaust) and performance related problems. Low oil creates possible mechanical failures that may not cause emissions problems right away. Best , is to stop running it and have it towed to a repair facility for diagnosis. If it's knocking , and you've already put the oil back to it's proper level , then internal damage has most likely already occurred. Continued running/driving it may make it unrepairable.