My stool has a groove in it, almost like someone scraped a line with a toothpick. should i be concerned?

No : I don't think you should be concerned. However, if you notice that the stool caliber is becoming thinner or if you see blood in the stool/from the rectum or if you have new change in your bowel movement/ worsening constipation, weight loss etc in addition to the above-especially if you have positive family history of cancer- you should see and discuss with your doctor as soon as possible.