I had a deep pimple on my chin and i knew not to pop it but i felt as though i needed to relieve pressure. now there's a large bruise under my chin?

Hands down: I agree, you should not have manipulated the pimple. Next time, if the pimple is sore, try applying a warm cloth to the surface of the skin gently. A topical acne preparation like benzoyl peroxide would be helpful. The bruise will resolve in about a week. Bruises arise from the rupture of blood vessels beneath the skin. Prompt pressure and ice can minimize bruising just as they begin to form.