Just had oil changed, dipstick reads full, but oil light flickers

The light is probably sending an OIL Pressure drop warning ---there is a rarity however
an oil filter may be improperly installed or the OIL Pressure connection on the oil pressure
sending unit --usually next to the filter --is loose or corroded or the oil pressure sending unit may
be going bad ---on a 2001 it is conceivable
otherwise you have an internal oil pressure leak --crank or cam bearings --bad o ringy thingy somewhere or the oil pump --may be experiencing problem too or the pick up screen in the oil pan
is somwhat clogged ---for a clog --try what's called SEAFOAM in the oil ---the stuff actually works
like it says on the can --about 8 bucks --drive for a week --say 500 miles worth and change the oil filter again --just the filter ---either way OIL Pressure is nothing to ignore ---you need to fix that
asap depending on the problem source!!!
I hope this helps
HAWK