Figure shows a small loop carrying a current I. The curved portion is an arc of a circle of radius R and the straight portion is a chord to the same circle subtending an angleq. The magnetic induction at center O is

Due to current shown in figure, the magnetic field within loop is outwards. So field at O should be inward because magnetic field lines form closed loop. But if θ > π, then point O will lie within loop and for a point within loop magnetic field is outward.