It's always like this at first. My finger hurts, and later, my wrist may hurt. If I write big letters with my elbow hanging, I will probably have shoulder pain, low back pain, hip pain and so on. This is a process. I am a calligrapher, and I am almost eighty years old. This process has passed. I am in good health now. Now write every day, or stand up and write. Calligraphy is the first longevity activity. Use your brain, do it, keep your health and your heart. I hope you stick to it all your life.
The problems you encounter are all common and don't need special treatment. It's like practicing martial arts. It's hard at first, but it's good when the kung fu comes. Of course, we should pay attention to interval rest and adjust our activities appropriately, and we will be fine.