Oil dipstick very hard to remove and insert.

[komichal]

If you remove the O ring, does it get better? Definitely not advisable to drive it like that but if the clean-up and oil-up does not help you may need to replace the O ring. Some people tend to add various shits to the engine oil and it may have caused the O ring to swell. Just guessing.
You can also try to swap the dipsticks with your co-worker to identify whether the problem is the dipstick or the engine.