Wait, when you say 'cant do anything doing with enemies+health' do you mean you:
1) Can't make enemies
2) Can't give them health
If it's (1) then I suggest you get working on an enemy to experiment with (jump on it to hurt it etc.). There's no point on doing a boss battle, if it's in the same vein, if you can't do a normal enemy. Or go for a platformer without boss battles.
For (2), I don't see how you can't. If each enemy is a self-contained object (which is should be), you should be able to house local variables for health that deteriorate everytime he/she/it is damaged.