I have been on Tamoxifen now for about a year. I did experience some side effects but they diminished over time. I got swollen hands and feet and certain joints became painful. At first, I got "trigger fingers" in my thumbs which were painful. Still over time, those side effects lessened considerably. Now my thumbs are perfectly fine and I don't really have painful joints anymore. Even the swelling in my hands and feet has gotten much better. Now, I would say half the time, I don't have any side effects at all. I never have a day that I would even consider my side effects to be anything more than a nuisance at worst.
I am assuming that you are ER/PR positive and that is why your oncologist wants you to take Tamoxifen. That is why I am on it.