Bro I had gone through this in my world as well but I used the method below and it worked for me but it was unethical and also very very risky. I just did it in the nick of time. WARNING: Try at your own risk! Just go to any browser and download a autoclicker. Then open the autoclicker and select the left click and set the frequency to as high as possible without actually making them unregistrable. Hold down the W-key while doing this and do NOT sprint. It should buy you enough time to knock the piglin far off. Open the settings again by ESC-key. Now, you have to set your hand on the keyboard and click the bone block items in your hotbar by pressing the recpective number button. Use the autoclicker and set it to right click with same frequency and press the S-key to go backwards and swing your cursor up-down as quick as possible if you have space behind you/incase not use the left click setting and look down to mine at least 5-8 blocks. Now, wait for a while and press ESC-key. Select the right click in autoclicker and exit settings look upwards and block with bone blocks. Now this has to be done with very ease otherwise you will sure shot lose your world. But its a risk worth taking.