I had the same problem myself with my son who's now 9. It's easy to say keep putting him back to bed and go through the crying barrier, but sometimes its easy to give in, especially when you need matchsticks to keep your eyes open. I was very often too tired to keep putting him back to bed and so most of the time we allowed it. Eventually, he grew out of it and wanted his own space (my son was about 4 when this happened).
Lady_p_gold has offered good advice if you've the energy to use it. But if not, don't worry. He'll grow out of it and certainly well before he's 18, lol.
Can you wait until he's fallen asleep in your bed and then move him into his own. I know its the easy option, it just depends how much patience you have.