If you can't rotate it out then "bouncing" it is the next stage
Wet the joint touroughly
Support both ends of the mast at a convenient height for you to bend the mast at joint.
Make sure the ends are padded where the mast rests on the support.
Now the fun part.

Using you body weight start flexing the mast at the joint. Whilst doing this occasionally rotate the mast.
After a while you will notice a gap starting to form bewteen the sections, keep going, add more water if drying out.
When gap is about 3mm try rotating your mast, it should be a bit looser, if not resume bouncing.
Normally takes between 5-15 mins and is a good aerobic work out.

have fun
Alby