Second only to water, a first aid kit is probably the most important thing to bring on a hike. It can include a lot of equipment, but there are essentials that every first aid kit should have:
Bandages and ointment:
The usual stuff for scrapes and owies. Always have a variety of sizes.
Aspirin, non-aspirin, ibuprofen, aspirin with caffeine. All good things to have. Search online for boxes of one-dose packets. That way you won't have bottles rattling around in your backpack -- and your can throw some packets in your glove box.
Usually referred to as moleskin, this thick padding will protect a blister or hot spot from further rubbing.
Cortisone, aka, itch medicine:
Because someone will get bit by a bug. Speaking of which...
Tick removal supplies:
A good tweezers and some alcohol wipes (for wiping down the skin after tick removal).
Buy a small first aid kit at the drugstore or, more economically, purchase your own supplies and assemble a kit. While you’re at it, make a larger one that you can keep in your car. Search online for first-aid kit checklists. Don’t forget toilet paper and a sanitary shovel.