Yes, I understand, I have been through this as well.
Can you see that he might think the same way how you feel
now?
Whether this friendship is worth enough to end for this reason, you
will have to think.
Apart from all this, you have to ask yourself, are you serious
about the person that is already attached? If so, I can say you
will not chase her this time. You want to chase her but somewhere
in your heart says its wrong. That's why you post tis topic
initially?
Ask yourself why your heart says its wrong?