Knocking in 98 Wrangler 4cyl

I was driving down the highway when i started hearing this knocking sound. pulled off the highway and parked. the first thing i noticed about the knocking was that when pushed the clutch in and the motor was able to move freely the knocking sound got alot louder and slowly got quieter as it got closer to idle. I open the hood and the knocking sound was definitely comming from somewhere in the block and was louder on the spark plug side of the engine. I asked a buddy of mine what he thought and he told me to hope it was top end. haha. so i took the valve cover off and unfortunately there was no broken parts, push rods, rocker arms and springs were all tight and i didn't see any visible cracks. Basically I'm just hoping someone else on here has had this same problem and could help me out. As above I drive a 1998 wrangler SE with a 4 cyl, 2.5L engine manual tranny and has about 84,000 miles on it. This is my only transportation and any help would be much appreciated.

Try a compression test on the cylinders.

haha i have no idea what a compression test is. would i have to get that done at a shop?