my question is,should I pot it on to a bigger pot, or is it too late now?
What size of pot is it in?
No it is not too late to repot providing you do it carefully i.e. do not disturb the root ball or break the roots.
The best way to do this is put a pot of the size your lily is in now into a larger pot. Pack compost around it then remove it.
This should create a hole of the right size to receive the rootball when you move your lily from its current pot.
On completion of this task give the new pot a good soaking and all should be well.
At the end of this season remove the bulbs from the pot and divide them if necessary and plant them immediately. In this way you will be ready for next years flowers.