What can i do about this pain in my achilles' tendon?

Stretch!: Make sure you do your warm-up and cool down stretches consistently. Check your shoes and make sure they are not wore out. Adding an arch support or heel pad may be beneficial. Temporarily hold back on your exercise intensity or duration. Ice, use of antiinflammatory medication such as ibuprofen can help. If these things do not work, of there is swelling and difficulty walking see a podiatrist.

Rest and rehab: The problem with achilles tendon is the poor circulation for healing. So it takes longer to heal than other tendons or muscles. First rest and ice the tendon to reduce the inflammation. Then stretching(dynamic and static) to reduce the tension on the tendon that causes it to get sore. First get eval by a podiatrist then they will guide you when physical therapy is right.