Rajan Natt, 20, told friend Kelly Shoker to delete the messages to her in the wake of Rezwan Ali’s death.
Mr Ali suffered a cardiac arrest after he was stabbed in the kitchen of a property, on Willows Road, in Walsall, on January 14, 2018.
Natt, of Castle Street, West Bromwich, denies any wrongdoing.
Miss Shoker, a witness, told jurors at Birmingham Crown Court that Natt contacted her through his sister’s Instagram account after the party.
She said: “I think he didn’t have a phone.
“He was really upset by the whole situation.
“He told me about about how he was arrested and how he was taken out of his house really early in the morning.
“It upset his family and him.
“He was saying ‘did you not see me? I was stood in the kitchen next to the window looking out to the garden’. I was like ‘I didn’t see you’.
“He told me to delete the Instagram messages he sent to me on his sister’s account.”
Miss Shoker said different groups were at the house party where trouble broke out before Mr Ali was stabbed.
There was an incident where someone’s mobile phone was taken by one group, jurors were told. She said a fight broke out in the kitchen between the same group and another man, but she did not “remember too much” of Natt’s involvement.
Asked by Mr James Curtis QC, prosecuting, about when she first saw Mr Ali, she said: “I didn’t see him until he was injured on the floor.”
She recalled seeing Mr Ali’s “white chunky” shoes and jeans, as he lay on the floor, but did not know it was him at the time.
After the house party, she had five missed phone calls off Natt which she did not expect.
Her friend, a woman, had organised the house party.
She told jurors that Natt has been invited to the party but Mr Ali turned up without an invitation.
The party had started for about 10 people but up to 60 people eventually turned up after it was advertised on social media, said Mr Curtis.
Earlier in the trial, jurors heard Mr Ali had been killed following a trivial row between two groups of young men.
Mr Ali was stabbed three times in his chest and arm including a four-inch wound to the heart which severed a major artery.
The trial continues.