Hi it would be good to see your foot in standing position as well. The way your foot bears your body weight will affect the pain that you feel. Rest and certain exercises will definitely help your condition however for a long term solution I would advise you to add corrections to your footwear which would prevent this from happening again. Also if your foot alignment is disturbed you would require some postural correction as well so you do develop knee or back pain in the future. If you have just started walking so many steps I would suggest you progress gradually rather than doing 8k steps directly.

If you could elaborate a little more on your pain. Also I would like to know how have you progressed your walk. It would be better if you could see a Physiotherapist so that the best treatment can be decided.

This condition is known as plantar fasciitis... atleast 7-10 days of physical therapy is required..if possible try to change it footwear which gives you a support and arch.. taping may required.. ultrasound and ice will definitely give you a good result

Plantar fascitis is the common cause for pain. you need physical therapy treatment, rest, ice if pain is severe and supportive shoe depending upon condition.

This problem is known as Planter Fasciitis.

You can perform these exercises https://youtu.be/GL9EyROxQgM