|Sure it is!
Open up the can and look inside. If there is a skin over the liquid, then carefully loosen up the edges with a stick then scoop the round piece of 'skin' out. Try not to leave any in the paint. What is left, if it isn't lumpy is Ok to use for a small job such as a repair or a patch. Hopefully there are the formula numbers still written on the can somewhere so you could have some mixed if needed.