I don’t recall seeing this plant before. Possibly a gift from the birds, or from Hurricane Irma? It’s growing in a pot with a rose in it, and seems to want to be a groundcover?
your plant appears to be a weedy introduced species named Calyptocarpus vialis, the straggler daisy. It has been recorded in SC previously, but it was not mentioned in the older flora books for the area. I have seen it more commonly in the deeper south, such as in Florida and Texas. For a great match to your picture, see: https://plants.usda.gov/core/profile?symbol=cavi2
Steve Hill, Ph.D., botanist, SCNPS