Hi, thanks for your question. It sounds like you have already seen a doctor and been diagnosed with phimosis and have been told to do stretching as part of the treatment. If  this is not the case, then please consider seeing a doctor for an assessment of your condition and if stretching would be useful in your case. If you have already seen a doctor and stretching has been suggested, then it is done gently together with a prescribed steroid cream. If there is swelling and pain that does not go away, you should stop doing any stretching and seek medical assessment as soon as possible.