President Carter and Nigeria's chief of state, Lt. Gen. Olusegun Obasanjo, yesterday discussed ways to increase U.S. business investment in the west African nation. At the same time, Carter asked that Nigeria help hold down future oil price increases.

As they ended two days of meetings, Carter called the sessions "a great stride forward" in U.S.-African relations. He said that "recognition of Nigeria as an enlightened . . . nation has been a long time coming."

"A year ago there had been acrimony between us, but now we have friendship," Carter told reporters after escorting Obasanjo to a waiting limousine. "I'm very gratified for the change that has taken place."

He was referring to the cool relations that existed between the United States and Nigeria during the Nixon and Ford administrations and to Nigeria's refusal three times last year to allow then-Secretary of State Henry A. Kissinger to visit the country-s capital, Lagos.

Obasanjo said at the end of yesterday's meeting that a "new chapter of friendship has been developed in the history of relations "between the two countries, a White House spokesman said.

The spokesman, Jerrold Schecter, said the two leaders discussed the possibility of setting up a join U.S.-Nigerian economic commission and to hold a seminar of business leaders from each country before Carter makes a state visit to Lagos Nov. 24.

State Department sources said a joint economic commission was discussed with a previous Nigerian leadership in 1975 but that little interest had been shown in the idea until recently. Nigeria is in the midst of a give-year development plan that calls for some $68 billion in public sector spending.

Carter also asked obasanjo to help hold down further oil price increases. Nigeria, which produces 2 million barrels of oil a day, is second only to Saudi Arabia in suppliying oil to the United States. Schecter said Obasanjo agreed to consider Carter's request.

Nigeria is a member of the Organization of Petroleum Exporting Countries, the 13-nation oil cartel that has quadrupled world oil prices since 1973.

After meeting with members of the Senate Foreign Relations and the House International Relations Committees, Obasanjo, spoke at Howard University, warning of "the explosive situation in souther Africa."

He said that in Rhodesia, Namibia (Southwest Africa) and South Africa, "Millions of blacks and Africans are suffering under colonialism and the most perverted from of racism-apartheid. The present United States administration has moved closer to us in finding solutions to these problems, and deserves to be congratulated."