How was the 11th Doctor able to repair hand of River Song?

In the episode Angels Take Manhattan of Doctor Who (2005), River Song got her hand broken while freeing herself from a Weeping Angel. Then, The Doctor used his regeneration energy to repair it. I remember River Song scolding The Doctor for wasting his regeneration energy.

I have two questions regarding this:

1. 
   

   How was The Doctor able to use regeneration energy while not in regeneration phase?

   
   


2. 
   

   How did The Doctor get the regeneration energy when he already used all of it in his own regenerations (12 regenerations including the War Doctor and 10th Doctor gaining same body had already been happened)?