Judging from this particular passage of the Qu'ran, there is a distinction between "Prophet" and "Messenger," just as there was made a distinction between Moses, who is considered as having been both prophet and messenger, and Jesus Christ, who is only a prophet. In the passage cited above from the Qur'an, Muhammed has the distinction of being only a warner, who bears no signs and wonders.
And, yet there seem to be some contradictions in the Qu'ran as to whether Muhammed is simply (innama) a messenger.
“O people of the Scripture! Indeed Our Messenger has come to you, expounding to you much of that which you used to hide from the Scripture, and forgiving much. Undoubtedly, there has come to you a Light from Allah and a clear Book.” (5:15)
Muhammad is not the father of any of your men, but (he is) the Apostle of God, and the Seal of the Prophets: and God has full knowledge of all things. S. 33:40 Y. Ali
Judging from histories written about Muhammed, he clearly perceived himself as a messenger since one day during his meditations as a young man, he reported having heard "a voice from on high" declare that he was the messenger of Allah. Further manifestations of this sort convinced Muhammed that he was hearing from the archangel Gabriel (Jibril), the same angel who had announced the birth of Jesus to Mary in the Christian faith.
In order to assuage this contradiction, it can be argued that Muhammad’s role as a warner automatically included his role as both a prophet and a messenger because the Quran itself testifies that prophets and messengers were also warners:
Mankind were one community, and Allah sent (unto them) prophets as bearers of good tidings and as warners, and revealed therewith the Scripture with the truth that it might judge between mankind concerning that wherein they differed..... S. 2:213 Pickthall