Maybe both. It's been shown that people in pain are distracted by the pain. The mind and body have a limited number of resources to complete each daily task. Pain is a stressor that automatically takes a certain amount of your energy and concentration.

A recent study of chronic pain patients showed that pain does have an effect on your ability to process mental tasks. With some part of your focus on the pain (even if it's subconscious), there's less attention available for tasks you must do at the same time.

Chronic pain patients tend to react quicker during tasks. This is true whether the task is easy or hard. It could account for the number of mistakes you are making even though you are doing a simple, but repetitive task.

It's not clear if slowing down and concentrating more would make a difference. Knowing there's a link between your pain levels and the number of errors you make may help remind you to slow down. See if it makes a difference. If you haven't explored all options for pain relief, further treatment may be helpful for you.