I have a pus or pimple near my private area and and it has burst. I wash the area before my wudhu then did wudhu so after my salat I saw little brownish from that pimple or puss in the toilet paper that I put on the area of pus or pimple. In this case did I need a new wudhu or my salat was valid ?

Your salat is valid and you do not need a new wudhu based on what you describe