Anyway to counter pantheon with nasus

Just lifeheal back all his poke from hitting minions?

I am a Gold 5 Nasus Main for context.

I don't know how you build or if you have a few rune pages for Nasus but I run Hybrid Pen Marks, Health/lvl Seals, 6 flat CDR and 3 scaling CDR Glyphs and Armor Quints. Masteries 12/0/18 with Grasp or 18/0/12 with Warlords. Start cloth +4 pots or Doran's Shield +1 pot.

Play passive early. Remember if he goes in to auto or trade then your minions aggro him. Just back off behind your minions and let them do work. Sip on a pot if you need to but try to only go for safe stacks where he can't combo you with his stun without taking a ton of minion/turret damage. He naturally pushes b/c he wants to harass you and get a kill try to freeze the wave right outside of your turrets aggro and just farm. I don't care how much farm you lose but don't give him a kill or your team will suffer. if you are under half health and you have no pots, Pantheon has full mana and is level 3 or 4 THEN B AND GO TO BASE! The other side if he's out of mana he can not really hurt you. Feel free to stack and AA to top off your health at this point. Even if he stays to farm he can not really kill you, as long as you are at 75% health or higher.

Rush IBG and Ninja Tabi. Once you have these he can not kill you without help or you overextending under his turret. At this point the lane is yours. Call out mia if he's missing as his ult will allow him to make big plays and you can not follow without TP. If you can TP and you are decently farmed and have an item or two and didn't die then go and help your team. Wither is hugely crippling to his damage and makes him easy to kill. He falls off hard the later the game goes b/c of armor and health being built and his scaling plateauing.

Hope this helps!