Listen to your chiro-he is right.
I get this very often, always after twisting the back when sweeping, raking, bending and twisting, etc.
In my case, the pelvic point locks up, restricting movement and causing pain and inflammation.
The chiro will be able to spot this problem by looking at the area while you lift each leg in turn.
Very easy to fix, and one treatment should do it.
Be aware though, that for a while afterwards the joint will still be liable to lock up again, as the tissues calm down.
So you must avoid any back twisting.
Nothing else will fix it-force must be applied to get the joint to unlock.
Physios and doctors will be of no use.

Forget all that rubbish you hear from people who don't get regular chiropractic treatment, or have no first hand knowledge. There is no magic or unproven treatment involved.
This is a very common problem, especially as the body ages and muscles lose tone. The spine then takes more of the strain that the muscles used to take, and problems quickly occur.
One you are fixed, you don't have to go back unless you feel the need.
However, you will likely find that they suggest a routine maintenance treatment to keep the spine in shape and to stop it getting stiff.
Up to you.
I do this every 3 months. But for the lockup thing I will see him 3-4 times a year just for that.
You may need to ask him about playing tennis, and what muscle strengthening exercises may help.
I think that once you have this problem with the pelvis, it is more susceptible to a recurrence the more often it plays up.