If it's a snapping turtle, at 2" long, it was probably born last fall, overwintered under ground, and came out recently. They are about an inch long when born.
The best thing to do is to release the turtle. If you keep the turtle, see http://www.fishpondinfo.com/turtles/hatchling.htm
for care information. They only want to eat small live animals like live blackworms at first. Small bugs from the yard are ok if the area is not sprayed with chemicals. Snapping turtles won't eat fish food or grass. My pages have information on proper setups and also photos of baby turtles to see if yours looks like the other baby snappers.