If you come upon someone who's been bitten or stung by an insect, you want to get them away from the area where the bugs are. You want to get them to a safe place, to prevent any further stinging. You're going to want to move the stinger, if there's a stinger in there. The best way to do that is to take some tweezers, and just pull the stinger right now. You don't want to squeeze it to try to get it out, because that could just push it more in. And it will release more venom. You want to clean the sight with mild, soapy water. You want to put an over the counter cream on it. You can get anti itching creams. You can get bug stinging creams over the counter at the drug store.
You may want to take an antihistamine. So over the counter, take one or two of those to help the swelling go down. You may want to take over the counter pain medications to help with the pain. If the area around the sting of the bite swells up to be large, larger than a baseball, you're going to want to seek treatment. You're going to want to call your doctor, go to the ER, go to an insta-care. Get someone to take a look at it. For severe reactions, you're going to want to call 911. Some people are very allergic to bug bites, and bug stings. If the person is having difficulty breathing, is confused, feels like their chest is tightening, gets dizzy, starts to have hives all over their body, gets nauseated, starts vomiting. You're really going to want to call for help right away.
If someone knows that they're allergic to a bee sting, or certain type of sting, and they have an allergy kit with them, get the allergy kit. They'll have like a epi pen or something like that. Follow the instructions. It'll tell you what to do. You're also going to want to loosen any tight clothing to help the person breathe better. If the person is starting to get dizzy or starts to lose consciousness, you'll want to help them to the floor. You want to roll them on their side, and keep them on their side. Especially if they start to vomit uncontrollably, or they're bleeding anywhere. That way they won't choke on their own vomit, or blood, and it can fall to the floor.
As you're waiting for the ambulance, if you see the person's not breathing, or you don't feel any kind of pulse, and you feel comfortable, you need to start CPR. If you don't feel comfortable, talk to the dispatcher. They can tell you what to do, and they can walk you through it as you're waiting for the ambulance to come to help your friend.