No, this isn't a contradiction -- and in fact it points us to a very profound and wonderful truth. Let me explain.
When Jesus Christ died on the cross, He became the final and complete sacrifice for our sins. He was without sin; throughout His life He never committed a single sin -- not even one. But on the cross the sins of the entire human race were placed on Him, and He took upon Himself the judgment and hell that we deserve.
He took our place! We can barely imagine this -- but when He died, God's own Son endured even hell itself on our behalf. This is why He cried out from the cross, "My God, my God, why have you forsaken me?" (Mark 15:34). This is what the ancient creed means when it says that "He descended into Hell."
But He didn't stay there! All those sins that were placed on Him were purged, and He entered heaven on our behalf. That is why He could say to the man dying on the cross next to Him, "I tell you the truth, today you will be with me in paradise" (Luke 23:43).
And this is what He says to us as we stand at the brink of eternity, if our faith and trust is in Him. Have you opened your heart and life to Him (as the criminal on the cross did), and are you trusting Him alone for your salvation?