Whilst changing the jockey wheel, consider getting one with a pneumatic tyre. I did when mine fell apart, and it is now much easier to move around by hand on uneven groung & gravel.
Regarding what made it sticky. Have you moved the trailer with the wheel wound well out? I imagine that you do not move it up and down on the clamp with all that nose weight. If you have you may have bent the "bolt" inside which will make it hard to turn.
An alternative way to reduce nose weight is to move the boat back on the trailer and then adjust the winch post and snubber.
"A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools" Douglas Adams