Bee stings are quite common to see in dogs at this time of year, and most often you will see a red swelling and it can be quite sore. The best advice is to come in and see a vet to have an anti-histamine or steroid injection which settles the sting down quickly. If you can't get to a vet then a normal antihistamine tablet can be given until you can see a vet, just make sure to call a vet for the correct dose.
Occasionally a sting can cause an anaphylactic reaction so if your dog collapses, has swollen ears, hives, has breathing difficulties or is very weak, please get to the vet immediately.