Tung oil is notorious for this....I use it a bunch on refinishing projects. The trick is, once you open the can, don't re-seal it with air in it. How do I do that? Pour marbles into the container to take up as much space as possible that resulted from the loss of the tung oil you used. You want that tung oil to be eaven with the top when you seal it off.
Good luck...and go buy you a new can of it..the jelled stuff won't work properly now. Those are the resins that are mixed in with the pure oil that have hardened with the exposure to air. The rest of the liquid is more or less the tung oil itself, which needs a hardener to dry.