Tendinitis is a painful condition of a tendon involving an inflammatory mechanism; it is a tendinopathy. It can be found in the Achilles tendon, the fascia of the foot of the long lateral fibular and toe flexors.
Tendinitis is commonly caused by repeated stress, supported or intensive. It may appear in athletes, workers who make repetitive movements or in a person who has an intense and inappropriate movement.

Your podiatrist can suggest several treatments including laser analgesic treatment, taking anti-inflammatory/analgesic drugs, some manipulations using neuro-proprioceptive  tapping or rehabilitation exercises.