Let \(1<c<\frac{127}{113}\) be a fixed number and N be a sufficiently large real number. In this paper, it is proved that the Diophantine inequality \(\begin{aligned} \left| p_{1}^{c}+p_{2}^{c}+p_{3}^{c}-N\right| <\varepsilon \end{aligned}\)is solvable in prime variables \(p_1,p_2,p_3\) such that \(p_1=x^2+y^2+1\). This result constitutes a refinement upon that of Dimitrov (Ramanujan J 59:571–607, 2022).