John 20:17 Jesus said to her, "Do not cling to Me, for I have not yet ascended to My Father; but go to My brethren and say to them, 'I am ascending to My Father and your Father, and to My God and your God.' "
NKJV

We could also use the NIV or NASV or RSV. Most good recent translations use the word "hold" or the word "cling" for the verb in Jesus' admonition to Mary. He is not making an issue of anything about his body - she probably had already taken hold of him when he makes the statement (Matt. 28:9)- but of the fact that he is not going to be available for that physical clinging which she emotionally desires. Rather, he is going to go to the Father as he had already predicted.

Since A. T. Robertson takes the same approach, I'll offer his comments from "Word Pictures in The New Testament", complete with transliterated Greek and Strong's reference #s.

John 20:17 Jesus saith to her, Touch me not; for I am not yet ascended unto the Father: but go unto my brethren, and say to them, I ascend unto my Father and your Father, and my God and your God.
Touch me not mee (NT:3361) mou (NT:3450) haptou (NT:680). Present middle imperative in prohibition with genitive case, meaning "cease clinging to me" rather than "Do not touch me." Jesus allowed the women to take hold of his feet ekrateesan (NT:2902) and worship prosekuneesan (NT:4352) as we read in Matt 28:9. The prohibition here reminds Mary that the previous personal fellowship by sight, sound, and touch no longer exists and that the final state of glory was not yet begun. Jesus checks Mary's impulsive eagerness.
For I am not yet ascended oupoo (NT:3768) gar (NT:1063) anabebeeka (NT:305). Perfect active indicative. Jesus is here at all only because he has not yet gone home. He had said (John 16:7) that it was good for them that he should go to the Father when the Holy Spirit will come through whom they will have fellowship with the Father and Christ.
(from Robertson's Word Pictures in the New Testament, Electronic Database. Copyright (c) 1997 by Biblesoft & Robertson's Word Pictures in the New Testament. Copyright (c) 1985 by Broadman Press)

Jesus instruction to Thomas to reach out and feel his hands and side a week later (John 20:24-29) neither contradicts the statement to Mary, nor does it indicate any change in Jesus' status during that week. Different verbs, different actions and emotions, different needs. Mary needed to not cling to Jesus' body, Thomas needed to verify that it really was his body. And then after 40 days Jesus did in fact ascend to the Father (Acts 1:3-11) as he had predicted.