Well, we have muscles that attach all the way up to our skull and onto our head. Perhaps you were straining during lifting and one of those muscles popped or stretched, etc. and this created a headache which was actually an ache due to the muscles in that area or where they attach? I was in a car accident and there is a spot that is up and behind my ear. It's where things attach and it can ache and ache which feels like a headache. Anyway, if you are not feeling anything anymore, you can either see your doctor to be sure or just resume slowly as you are. Let us know how it goes!
This has happened to me often over many years. Don't think it's anything. It was probably from the neck. Just be sure when you lift you do it with proper posture and breathing and aren't lifting more than you can handle so you aren't over-stressing.