1) Find and fix the oil leak
2) Make sure oil level is correct
3) Make sure idle speed is set correctly and the idle control valve is clean and functioning to maintain steady idle.
If the light still flickers after you do the above, then we have some more troubleshooting to do. I suspect this will cure it though.
Current ride... '13 GTI Wolfsburg
BMW's from my past...
'92 535i/5 '89 325ix/5
'98 750iL '86 325(e)/5
'95 740iL '84 318i/5