Knocking/Pinging in 99 Ram 5.2

I just filled up on gas(87 octane) and took my Ram thru the automatic car wash, which was a very rough car wash(soft cloth but very high pressure). Anyway when I left I noticed upon acceleration that the engine was hesitating a little and making a light knocking/pinging noise. I popped the hood and it sounded as if it we coming from the driver side of the engine. After sitting for 2 hours it now sounds normal. Any ideas on this? Would bad gas cause a pinging immediately, or could the car wash just soaked everything and caused this? Any input is appreciated. Thanks!

99 Ram 318 4X4