Let's look at this logically. First, though, if you have an oil pressure
LIGHT, you do not have an oil pressure sensor, you have an oil pressure
switch. It is either on or off and it can fail electrically or it can leak
or both.

You say you have plenty of oil and that when you took off the oil filler
cap some splashed out on you.

That means that you DO have oil pressure because it is a LONG way down
to where the oil is in the crankcase and it doesn't just come up there by
itself. So stop worrying, if you are getting oil all the way to the top,
the car is certainly safe to drive gently, even if not abusively.
(I would bet that your oil pressure is normal and your light is being turned
on by accident somehow.)

First, LOOK at your oil pressure switch. It is a little over an inch in
diameter and screws into the side of the block, probably near the oil
filter. See if the wire is hooked to the end of it. (Many have a yellow
wire here but yours may be some other color.) Examine the wire closely
to see if the insulation is damaged and touching something. The exhaust
system is a likely suspect because it gets hot enough to melt the insulation
on the wire and it is close by. If you don't see any damage there, unhook
the wire and start the engine. If the light is still on, then you have a
short in your wiring. If not, you probably need to replace your oil pressure SWITCH.

If that doesn't identify the problem, post again because there are other
possibilities (but not as quick or easy to fix).

--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma