I Was Gardening Today And May Have Pricked My Thumb

I was gardening today and may have pricked my thumb with a rose thorn, nothing serious at the time, didn't think anything of it. I noticed about 7pm that it was becoming hard and swollen, but again didn't think much of it, perhaps a splinter. Now the whole thumb I'd swollen, hard and throbbing and preventing sleep. Is it something serious that I need antibiotics for?