The meaning of 26-27 is made clear by the verses before and after.

Paul having earlier founded a church at Ephesus returns there on his way back to Jerusalem. Paul knoes he will soon be arrested and killed. He assembles the leaders and tells them

25 “Now I know that none of you among whom I have gone about preaching the kingdom will ever see me again.

26 Therefore, I declare to you today that I am innocent of the blood of any of you. 27 For I have not hesitated to proclaim to you the whole will of God.

28 Keep watch over yourselves and all the flock of which the Holy Spirit has made you overseers. Be shepherds of the church of God,[a] which he bought with his own blood.[b] 29 I know that after I leave, savage wolves will come in among you and will not spare the flock. 30 Even from your own number men will arise and distort the truth in order to draw away disciples after them. 31 So be on your guard! Remember that for three years I never stopped warning each of you night and day with tears.

In short, Paul also knows that the leaders of the Church at Ephesus are also in danger. Paul already informed them of their fate and that it is God’s will. Thus their blood is not on his hands.