Can you unload the thing? Start there. Even with blanks, you don't want one of those going off while you're messing with the hammer.
Then - with NO ammo in the cylinder, and the cylinder in the closed, ready to use position, can you pull the hammer back by hand, without using the trigger? I'm not really sure if you can normally cock a starter's pistol (allow the hammer to click into it's rearward position). It might be double action only (pull the trigger, the hammer cycles).
I would imagine the hammer has simply found it'self into half or quarter cock position. There's likely nothing broken. It just needs to be pulled back to it's rear most position to get it out of it's current state.
In single action guns (cowboy pistols) that position it's in is where you deliberately put the hammer in order to remove the cylinder for cleaning. It's a perfectly normal feature.
Again, get the blanks out of it before experimenting, please.
Sgt Lumpy - n0eq