What Causes Hand Heaviness, Numbness With Stinging Sensations?

2 hours ago, I was pulling weeds from my backyard. After pulling 1 particular plant, I felt a stinging sensation. Now, my hand feels heavy, numb, stinging and like I have many pins and needles. I took a benadryl and tried calamine lotion, 2 hours later and still no relief. What should I do?