Hornet Sting...on my boob

So, Friday afternoon I was cleaning my deck and opened the umbrella above the table. I no sooner start cranking it open and three hornets dropped down out of it...one going right down my shirt. I immediately felt it sting me and I ran back into the house, for my shirt off, and it had itself by that point between my cami and bra. I mixed up some baking soda and water, caked it on the sting, and grabbed a band aid to keep it in place. There was no stinger left in. Well, it started as a small rash, maybe a dime. The next day it was the size of I’d say a quarter. Today, the rash is even bigger and almost a whole side of my boob. I also noticed that nipple is almost constantly hard. The whole thing is SO itchy but thankfully it’s not painful. Has anyone else had this happen? I’m 26 weeks pregnant and am worried that the venom just kind of keeps spreading out more and more. I don’t usually post anon but it’s a little embarrassing and while I don’t think it’s something I need to be seen by a doctor for, if it continues to get bigger, I’m thinking I might call in to the OBs office and see if they are concerned about it at all. I did get stung last year on my thumb, also by a hornet, and my hand swelled pretty bad. I have no swelling that I notice but its difficult to tell on a boob...