Thanks to everyone who commented back when I asked for advice. I decided not to frog it after all, and just pulled those stitches tighter on the next rows. I guess I have tension issues between my knits and my purls. If this were a garment, I might be more concerned, but it's a doggone washcloth, after all -- why sweat it? I will also follow the recommendation to machine wash and dry it, which supposedly straightens out the stitches even more. I have also noticed that this yarn's dye is leaving some of itself on the tips of my bamboo needles, which tells me the washcloth definitely needs to be washed before I give it away.
I found the pattern on a great website called Dishcloth Boutique. And earlier today I stumbled upon another cool dishcloth pattern website called Knitting Knonsense. They even have another, different (easier!) shamrock dishcloth pattern here:
Wish I'd found this one first! Oh well -- the first one was good practice for me with its seed stitch and yarn-over-purl-2-togethers. Maybe I'll have enough yarn left over for this new one, too. Maybe....