What does Catholic Church say about the post-resurrection wound marks of Jesus? At John 20:24-27 (NRSVCE) we see:


  But Thomas (who was called the Twin), one of the twelve, was not with them when Jesus came.  So the other disciples told him, “We have seen the Lord.” But he said to them, “Unless I see the mark of the nails in his hands, and put my finger in the mark of the nails and my hand in his side, I will not believe.


A week later his disciples were again in the house, and Thomas was with them. Although the doors were shut, Jesus came and stood among them and said, “Peace be with you.”  Then he said to Thomas, “Put your finger here and see my hands. Reach out your hand and put it in my side. Do not doubt but believe.” 

My question is: Why was it necessary for Jesus to retain the wounds he had received at the cross, even after His glorious resurrection? Was it done to convince the disciples that it was Jesus Himself appearing before them, or was it a symbolic statement that Jesus continues to suffer for the sins of mankind? What do the teachings of Catholic Church say about the post-resurrection wound marks of Jesus?
St. Thomas Aquinas addresses the question of "Whether Christ's body ought to have risen with its scars?" in Summa Theologica III q. 54 a. 4. He gives five reasons (c.):


  It was fitting for Christ's soul at His Resurrection to resume the body with its scars.
  
  
  for Christ's own glory. For Bede says on Lk. 24:40 that He kept His scars not from inability to heal them, "but to wear them as an everlasting trophy of His victory." Hence Augustine says (De Civ. Dei xxii):Perhaps in that kingdom we shall see on the bodies of the Martyrs the traces of the wounds which they bore for Christ's name: because it will not be a deformity, but a dignity in them; and a certain kind of beauty will shine in them, in the body, though not of the body.
  to confirm the hearts of the disciples as to "the faith in His Resurrection" (Bede, on Lk. 24:40).
  "that when He pleads for us with the Father, He may always show the manner of death He endured for us" (Bede, on Lk. 24:40).
  "that He may convince those redeemed in His blood, how mercifully they have been helped, as He exposes before them the traces of the same death" (Bede, on Lk. 24:40).
  "that in the Judgment-day He may upbraid them with their just condemnation" (Bede, on Lk. 24:40). Hence, as Augustine says (De Symb. ii):Christ knew why He kept the scars in His body. For, as He showed them to Thomas who would not believe except he handled and saw them, so will He show His wounds to His enemies, so that He who is the Truth may convict them, saying:Behold the man whom you crucified; see the wounds you inflicted; recognize the side you pierced, since it was opened by you and for you, yet you would not enter.