Hi buddy, sorry to hear about your issues. If the pick up is new, then either you have a fault with the oil pressure switch/wiring or you have a
problem with the oil pump or worn bearings.
I would change the oil pressure switch and then go from there. I'm pretty sure it's next to the oil filter from memory.
If the light is still coming on when the switch is replaced and the wiring checked, then you need to get the oil pressure checked to see if it's low.