I have heel pain on the bottom after accidentally stepping on plastic object. no break in skin, no bleeding, color normal. pain to put pressure on it.

Bruise: This pain was apparently not present prior to the trauma. Suggest that this can be bruising if you came down hard on the object or overweight. and stepped down hard. Time and ice over this may help. Stay off for the next 24 hours for most activity. Note that if one is on blood thinners this may cause some blood under the skin or in the bursa.

Stone bruise: Sounds like bruising which should improve in a few weeks. If worsens or does not resolve by that time, please visit your primary care physician or podiatrist. If no allergy, liver or kidney disease, you may take Advil or Aleve (naproxen) to help with pain, and apply ice pack with skin protection of a towel.