Saa’i is one of the essential parts of ‘umrah, without which it is invalid and incomplete. If a person does ‘umrah and does not do saa’i and was not prevented from completing ‘umrah by an enemy or sickness that prevented him from completing his ‘umrah, then he is still in his state of ihram and he has to go back and do saa’i and cut his hair. This applies to the adult who is accountable. With regard to someone who is not an adult or accountable, the matter is easier. A number of scholars are of the view that his ihram is not binding, and whatever he has done will be accepted from him, and if he interrupts his ihram or does not complete his ‘umrah, there is no sin on him. This is the view of the Hanafis and Ibn Hazm, and was the view favoured by Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) among later scholars.
See: al-Sharh al-Mumti’, 7/21; Majmoo’ Fataawa Ibn ‘Uthaymeen, 22/148
Based on that, if you did this ‘umrah before you reached puberty, you do not have to do anything.
If it was after you reached puberty, and you did a complete ‘umrah after that, then the complete ‘umrah will suffice for the one that was incomplete. That is because your ihram for the second ‘umrah was superfluous, because you were already in ihram, so the saa’i and cutting the hair count towards the first ‘umrah, and thus your obligations have been discharged.
We asked Shaykh ‘Abd al-Rahmaan al-Barraak (may Allaah preserve him) about a woman who did ‘umrah and forgot to cut her hair, then she went and entered ihram for another ‘umrah and did tawaaf and saa’i and cut her hair.
He replied: Overlapping two ‘umrahs is not correct according to the fuqaha’ of the Muslims, so the second ‘umrah is superfluous, and her cutting her hair counts towards the first ‘umrah. End quote.
If your marriage contract was done after the valid ‘umrah -- as we understand from your question -- then it is a valid contract, because it took place after exiting ihram following ‘umrah.
And there is nothing wrong with you doing the marriage contract in the future.
And Allaah knows best.