Question: I'm currently playing a piece which requires big stretches of large intervals across the keyboard. It slightly hurts when I do so, and I am wondering if I should continue to practise like this.

[![Bartok Suite op14 - Allegretto](https://i.stack.imgur.com/6cfvl.png)](https://i.stack.imgur.com/6cfvl.png)

My piano teacher suggests fingerings with a combination of 3 1 and 2 1 in the L.H.

Answer: 
Don't persist in doing anything that hurts. 

As commented, if you show us the passage in question we might be able to suggest a strategy.
Since we can't see the score, and we don't know exactly what you are trying to do, it's hard to answer this, except by saying:

**Whatever you are doing, it is the wrong technique to play the piece, so stop doing it before you injure your hands permanently.**