I've gotten bit by something and it's been over 24hours with no improvement.

Watch it...: If wasn't something large like a bear but rather a spider or some insect it is probably ok to watch it unless it is getting worse, the redness is spreading out from the bite, you are running fevers, or red streaks going out from the wound just keep it clean and dry and follow up with your GP in a a day or two if no change.

Cool the area: most likely you describing a venomous insect bite , that can cause local reaction or generalized severe reaction (anaphylaxis) that need emergency treatment it can be complicated with local bacterial infection, urticarial (allergic reaction), persistent insect bite reaction for local reaction treatment is by cooling the area, topical anesthetic and oral antihistamine. and possibly antibiotics

Well need some info: When you say no improvement. Well how bad is it. The best thing would be to get medical attention

Bite: You may have an allergic reaction that needs benedryl and or steroids or it may be a brown recluse spider bite that can cause tissue damage .Would follow up in urgent care or ER today . You will also likely need an updated tetanus shot if you have not had one in 5 -10 years