Where exactly was this oil leak?
is the oil correct on the dipstick when checked? did they replace the oil/filter after the job was carried out?
The oil leak was at the sump,oil level is correct when checked.Oil was replaced but not filter.
Ok.... if that is ok as per your oil level - then other checks would have to involve checking the oil level/pressure sensor and its wiring fully to ensure these haven't become loose or the level/pressure sensor in itself hasnt become faulty - another likely problem could be oil pressure or circulation problem that normally why the oil low pressure warning flags up - you'll need a proper gauge/equipment to monitor the pressure to ensure it is indeed correct and the pump is in fully working order to circulate the oil properly at the correct pressure or via diagnostic machine to monitor it,the dealer would know the procedure to check that - Another likely cause could be inside the sump itself ie:- the pick-up/strainer is getting blocked slightly - the only way to check that out properly or fully is to have the sump removed from the engine again to get a better look and the pick up inspected and cleared out - once that's done and checked and everything back together - then the correct grade of new oil and oil filter can be fitted and then see if that makes any difference...i note you say the didnt do a oil filter change..that could be worth doing first and see if solves it..if not then they need to check oil pressure to rule either a problem internally as above or a fault pressure switch..i do hope this helps
Is it safe to drive.
If there are no unusual noises from the engine - rattling / or knocking i shouldnt see why not but this should be looked into as soon as possible to be honest...I do hope this helps further