Oh 
How old is your remaining piggie ?
I'm guessing uncastrasted adult boar ?
Were they are brother pair or different ages?
Is he indoors ?
First of all 100% leave the body a while so he can sniff about and know his cagemate is gone (we used to leave them overnight , and remove them before they niff)
Clean the cage of bedding but you don't need to do a complete scrub (unless he died of some infectious illness in which ase you'd need to take your remaining pig for a check up )
When GP2 died we phoned up rescues to find a piglet boar for GP1 . It took a few days , GP1 was alone for 6 days , we kept him in DD room.
You might find Rescues difficult at the moment but most will try and find you a match for a bereaved pig.
GP3 was 6 weeks old and boars are easier to find than sows .
When GP3 ( the piglet who grew and grew) was alone we got him sows and had him castrated . He was kept beside the sows but not allowed to bond for 6 weeks to go sterile .
Castration isn't without risk but the Rescue we got GP3 and GP6 from used to castrate the boars as standard , makes them easier to re home .
So it depends on the age and health of your boar if you want to castrate him. And if you get a piglet boar you need to manage a new relationship .An you're back in the same situation when you're back to one boar ( The Guinea-Pig Spiral 
)
When you do find him a friend then you do the whole scrub/neutralise of the cages , neutral territory to introduce .
Lots of food to keep them occupied and make sure they cannot trap each other in a hidey box.
Our GP1 was so delighted with GP3 , he did miss GP2 . But he did need a few days on his own with DD spoiling him .
Good Luck