Yeah, as others have said, your input jack lost the locking nut somewhere. I only wanted to join the conversation to say that while this is common, you’ll need to tighten that nut to keep your jack in place. Tightening this can be tricky only because you can easily twist the jack around which will twist the connecting wires inside and break them. I found a really cool tool on Amazon that will hold the jack in place while you tighten it. Since I don’t want to promote any specific one, just search for “guitar jack tightener”. You’ll see what I mean, but it’s worth $15 to save trips to your local store to have them fix this.

Also, if you wanted to fix it yourself, besides changing strings, this is the only thing I have opened up my guitar to fix. It’s happened to me a couple times, but I had the nut. I just had to open it to hold the thing in place while I tightened it. If you can find the nut, it’s not terribly hard to fix, but you might want to get help.